The quadrilateral ABCD is inscribed in a circle. It is known that ∠ABC = 155 °. Find the ADC angle.

Let’s use the property of a quadrilateral inscribed in a circle: “If a quadrilateral is inscribed in a circle, then the sum of its opposite angles is 180 °” => ∠ADC = 180 ° – ∠ABC = 180 ° – 155 ° = 25 °
Answer: 25 °

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